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Old 12th Dec 2018, 1:22 am   #127
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,482
Default Re: MK14 schematic revisions

I would actually be quite interested in an 'MK14.5' PCB which used a slightly later 8-bit wide RAM and EPROM.

Mapping the 6116 into the three areas occupied by the standard RAM, extended RAM and RAM /I/O but keeping it away from any other part of the range could present a challenge - could use a 74S571 PROM as an address decoder of course, but it would be better to shy away from devices which hardly anyone can program now. MK14man's project, although brilliantly executed, was problematic for the same reason, not many people have facilities for programming FPGAs and other programmable logic.

My original MK14 is almost too precious to run now, I keep thinking that the next power-on inrush will be the one which finally finishes off a vital component, so it would be good to have a second, expendable machine for playing with, but quite honestly the difficulty and expense which you and others have incurred while trying to acquire parts, get PROMs programmed and so on would really put me off building a precise replica.

Oh by the way, if you are feeling particularly enthusiastic, how about tracking the address, data and control buses to the fingers on the underside of the top edge connector? SOC never did bother to do that, but it would have been a very sensible thing to do especially after the introduction of the VDU, which required all those connections.

Last edited by SiriusHardware; 12th Dec 2018 at 1:30 am.
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